Aims/hypothesis. Overwhelming evidence indicates that endothelial cell dysfunction in diabetes is characterised by diminished endothelium-dependent relaxation, but the matter of the underlying molecular mechanism remains unclear. As nitric oxide (NO) production from the endothelium is the major player in endothelium-mediated vascular relaxation, we investigated the effects of high glucose on NO production, and the possible alterations of signalling pathways implicated in this scenario. Methods. NO production and intracellular Ca 2+ levels ([Ca 2+ ] i ) were assessed using the fluorescent probes 4,5-diaminofluorescein diacetate and fura-2 respectively. Results. Exposure of cultured bovine aortic endothelial cells to high glucose for 5 or 10 days significantly reduced NO production induced by bradykinin (but not by Ca 2+ ionophore) in a time-and dose-dependent manner. This was probably due to an attenuation in bradykinin-induced elevations of [Ca 2+ ] i under these conditions, since a close correlation between [Ca 2+ ] i increases and NO generation was observed in intact bovine aortic endothelial cells. Both bradykinin-promoted intracellular Ca 2+ mobilisation and extracellular Ca 2+ entry were affected. Moreover, bradykinin-induced formation of Ins(1,4,5)P 3 , a phospholipase C product leading to increases in [Ca 2+ ] i , was also inhibited following high glucose culture. This abnormality was not attributable to a decrease in inositol phospholipids, but possibly to a reduction in the number of bradykinin receptors. The alterations in NO production, the increases in [Ca 2+ ] i , and the bradykinin receptor number due to high glucose could be largely reversed by protein kinase C inhibitors and D-伪-tocopherol (antioxidant). Conclusions/interpretation. Chronic exposure to high glucose reduces NO generation in endothelial cells, probably by impairing phospholipase-C-mediated Ca 2+ signalling due to excess protein kinase C activation. This defect in NO release may contribute to the diminished endothelium-dependent relaxation and thus to the development of cardiovascular diseases in diabetes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations鈥揷itations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright 漏 2024 scite LLC. All rights reserved.
Made with 馃挋 for researchers
Part of the Research Solutions Family.